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DCC'ifying the MTH F7s


SteamPower4ever
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As I've written again and again elsewhere, I want to repower my F7s and fit DCC decoders and smoke units, so all the F7s will be pulling, smoking and making noise.

I'm starting from the rear - the slave A - and have taken it apart to get a feel for what is to be done. I have chosen speakers that protrude through the bottom of the body, so I need to reinforce the frame part somehow while still maintaining the weight of the unit. I was expecting that, so no biggie here, although right now I have no clue what I'm going to do. Probably some brass construction which allows room for the speaker and which includes attachments for the new NWSL drives. A bit of a challenge, but that's what I like.

 

One question:

That branched plastic tube thing that comes down from the roof - what is that used for?

It's in the center of the second picture and it looks a bit like a drain pipe ...

 

Jens

 

IMG_0576.JPG

 

IMG_0580.JPG

 

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3 hours ago, Chuck said:

I think that tube is supposed to represent the blower duct for cooling the front truck traction motors. 

 

Sounds very likely.

The weird thing is that it actually fit to a socket in the bottom of the body and there's a hole through. Like it's supposed to drain some kind of liquid. Why else bother making a hole?

Never mind. I'll figure out what to do with it.

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On 26. november 2016 at 11:26 PM, SteamPower4ever said:

IMG_0580.JPG

 

 

Since the tube doesn't really show from the outside I've gone ahead and cut it to free the smoke duct assembly. As expected, the tube does provide a vent from the space around the smoke duct and out through the bottom of the body, but it doesn't really do anything as the smoke ducts are isolated by gaskets.

The only thing I can think of is some kind of drain for condensed smoke oil that escapes from the ducts. So why the vertical part to the part of the roof where there's no opening? Probably just support.

Either way, the tube is history and I don't have to bother making space for it when I figure out how to arrange the new parts.

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  • 1 month later...

Hi there: I was just wondering why  on earth change the power trucks as I understand that the NWSL power trucks aren't worth much power wise and knowing from experience that the MTH ones are very good mechanically? Powerfull, smooth, with brass gears and bearings what could you want more? I personnaly have fitted NWSL wheelsets to my Lionel GP7 to equip it with scale wheels and also to improve power pick up as it does not have  pick up shoes. On my MTH PRR F3 I dismantled the wheelsets and turned down the flanges on my lathe to scale size or at least RP25 type profile so that it looks better and works well on my layout but I would never throw out that good a power truck. I have no personnal experience with NWSL power trucks but a good friend of mine did away with all the ones he had , after stripping the gears and burning out motors...

 As for the  forked tube in the bodywork I wonder if it isn't designed to drain any oily residue condensate from the smoke generator. I have cut out mine as I don't go for that kind of gadget myself. If you have seen what real diesel smoke looks like and what smoke units produce, It's not desirable. This of course is only worth my personal opinion. As I burned out my boards for the second time in three years, I actualy run my F3 in analog and both are now independent. both the slave A and the lead A, I also can MU with my GP7. But I may yet refit them with new boards as I like the advantages that DCS gives outdoor operators....

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Ahh, you know - I'm a tinkerer. It's fun - that's really all the reason.

 

Basically I want to get rid of the sliders. I always imagined I would do that, and after test runs on the layout(s) that for now will be the home turf, I'm right in doing so. They are causing shorts in some turnouts.

Next is to improve pickup as the MTH trucks have tires, which means that without the sliders I have reliable pickup on only two axles. Hence new trucks. I have good experience with NWSL in the past, although in smaller scale, so time will tell.

 

Edit: I'm powering the B units too, and they'll get NWSL trucks. I like to have the same drives in all units.

 

I too think the forked tube is some kind of condensate drain, but it doesn't originate from the smoke pipes but from the chamber surrounding the smoke stacks.

Anyway I'm arranging my smoke system so any condensate drains back into the smoke unit.

 

To get the best sound I've chosen the largest speaker possible. It's actually a Visaton FRS 8. It doesn't fit in the MTH frame, so I've cut an opening for it in the plastic frame.

 

IMG_0585.JPG

 

That of course weakens the frame, so I'm adding a brass plate, which first of all must have a similar hole for the speaker, and I'll reinforce it with brass profiles. I'll arrange those so that I can close the speaker chamber.

I'm also going to build some new mounts for the trucks. I'm working on a design for 3D printing.

 

IMG_0595.JPG

 

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  • 2 weeks later...

The pieces are coming together.

 

A 3D CAD program can also be used for lighter duty such as rough planning of an assembly. I've made models of the outlines of the MTH body and frame and crude models of the stuff I'm going to use, and it fits well together now.

Below is a model of the interior of the F7A:

 

- Light grey is the MTH frame (brass plate not shown, but included in the dimensions)

- Dark grey is the MTH weight blocks

- Blue is the speaker and truck mounts

- Amber is the brass supports

- Green is the ESU decoder

- Red is the ESU smoke unit

 

The two floating pieces above the model are the smoke stacks. Next I need to design some sort of duct work from the smoke unit to the stacks.

 

parts.jpg

 

There's room for the cab, except for the staircase at the rear of the cab, which has to go.

I've managed to use the MTH weights without modification, and now I just need to figure out how to make threads in them. The look and feel like they're made from more than just black iron. Steel or something.

 

Here's the truck mounts as ordered from Shapeways.

The upper part mounts in the frame and the lower part attaches to the NWSL truck, attaching the truck sides with the same four screws.

The two parts fit together like a simple key, which is turned 90 degrees to lock. Once the truck is in place, it can't swivel that much, so it stays in place and the frame rests on the crest of the lower part.

 

truckmounts2.jpg

 

As I said earlier, I think I need to strengthen the frame after weakening it at the openings for the speaker and the truck mounts.

Here's the frame support with a 1mm brass plate cut to shape and the brass profiles soldered to the plate. Once attached with screws (I haven't made up my mind about glueing it yet), the entire frame will be totally straight and rigid. That gives me peace of mind, as the MTH frame itself is warping, even before I started working on it.

 

IMG_0598.jpg

 

Jens

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The first parts arrived from Shapeways.

Out of the box, the NWSL trucks come with a small retaining ring that is supposed to secure the king pin to the frame. I think that's a bit too flimsy.

 

truck1.jpg

 

Because of difference in height and king pin location between the MTH and NWSL trucks I've made adapter sets for the trucks.

They're in two parts and one part attaches to the NWSL truck like a saddle.

 

truck2.jpg

 

The space between the tabs on the truck and the saddle are designed to fasten the truck sides.

Four screws and it's done.

 

truck3.jpg

 

The other parts go in the frame where I've cut the square holes.

I still need to cut holes in the MTH frame, but four more screws at either end and I'm done here also.

 

truck4.jpg

 

The trucks are then attached to the frame by inserting the tabs at the top of the saddle at a 90 degree angle and turning the truck to the right position.

The frame then rests on the shoulders of the truck saddles and when the crew stairs are in place, the trucks can't turn back to the detach position.

 

And the real beauty is that for the next four units I can simply order the parts ... B)

 

truck5.jpg

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Looking great as I do like the idea of a 1/4 turn and the trucks come off for easy maintenance! :)

 

Brass floor/ reinforcing looks nice too! Excellent soldering skills to keep all that from warping!

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Thanks, Chuck. I'm quite proud of the design myself :)

 

I've designed the smoke ducts that fit the ESU smoke unit. The part fits onto the screw posts in the MTH body and the exhausts match the MTH smoke stacks.

MTH has opted for a semi-open system with soft gaskets between the body and the smoke system, which is why they've designed that drain pipe to drain condensed smoke fluid away. I'm going for a closed system where I glue the part in place at the smoke stacks. Mostly to seal the system. Mechanical stability comes from the screws.

 

Here's the complete design. I can fill smoke fluid in either stack.

I lowered the smoke unit (red) a bit, which makes me think that maybe it should be attached to the frame after all. I'll have to think about that.

 

smokeducts.jpg

 

 

I've noticed on several videos of the ESU smoke unit that at low speed the smoke flows too smoothly for my taste. Looks like the smoke simply escapes unforced.

To stir up the smoke I've added some internal bulkheads in the ducts. Hopefully they provide some turbulence even at low speed.

Here's a cross section of the duct unit:

 

halfsection.jpg

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I'm waiting for parts, but meanwhile I've assembled the trucks.

The screws go in from below and I've made hex holes for the nuts, so the assembly is fairly easy.

IMG_0608.JPG

 

IMG_0609.JPG

 

 

Having considered pros and cons I decided that the smoke unit should be attached to the body part. The smoke outlet connects to the duct assembly with a small piece of rubber tube that comes with the smoke unit, and fitting those parts at the same time as matching the body to the frame is simply a no-go. There's no room to guide the parts in place and no way to assure they're in the right place after assembly.

So - after a few failed designs I've made some hanging brackets that should work well. The ducts are redesigned slightly giving more room below for the smoke unit. When assembling the engine, I just need to plug the connector from the decoder to the smoke unit.

 

sideview.jpeg

 

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I think that some engines have the smoke unit just close enough. On some models you'll find smoke oil all around the inside. So your idea seems best to me. You could have the four wire smoke harness long enough to separate the shell and then unplug it for more room.

 Thanks for sharing this. It's cool to see more modern drawings than my usual napkin drawings.

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Fixed the screw that was causing trouble and after a bit more work with the saw and drill, the frame construction is now done.

Now I just need to mount the belly tanks with the speaker, attach the wires to the decoder and it should be ready to growl B)

Notice the decoder is sitting on nylon stays to isolate it from the new metal frame. I may need a few drops of glue to secure the screws in those nylon stays. They feel kind of "not entirely fastened" and I'm afraid to overtighten them.

 

IMG_0614.JPG

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  • 1 month later...

So far it looks like a really neat job Jens, I am currently testing out running my F3 in analog, as I am no electronic wizzard and really don't have much electronic know how, I think that I will stick to analog running, more my generation... Added bonus now I can MU my A-B-A lash up of F3 with my Lionel GP 7 which I redetailed thanks to the help of XL special all the way from Vancouver Island through this forum and equiped with NWSL wheelsets.  As the weather today is raining I can't post a photo of this lash up in front of a 42 car freight but will endeavour to do so as soon as the weather permits. Way back four years ago I reduced the flanges on my lathe and I find the pick up shoes aren't too visible on the F units, and they do insure good pick up on my brass track. I have kicked out the sound... But have been able to wire back the lights, but they are not constant. MTH DCS is wonderful when it works, but it is a constant source of trouble for me, I have often run through 3 fusdes in one afternoon operating session. Plus all the protocol to light up engines on a dead track... I have to insulate my indoor yard because you can't see it from outdoors and I burned out two motors once which Raymond fixed for me because the engine which was idliing, went off into the yard throat after a short circuit on the outdoor and it sent the lead A unit into a switch which shorted it out while the trailing A unit kept pumping away forward until the motors burned out! I operated the layout for twenty years without DCS so it is back to analog for me, but regretfully as the possibilities of DCS are wonderful.

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  • 5 months later...
 

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